Manage your subscription

Wasps use parasitic mites as baby bodyguards

Video: Parasitic mites have been found to attack intruders in nests of potter wasps

Parents will go a long way to protect their children, and one type of wasp goes as far as offering a home to a parasitic mite that helps fight off intruders at its nest.

After breeding, potter wasps (Allodynerus delphinalis) build a nest and lay eggs inside cavities that contain food and are sealed with mud and saliva. But the insect’s offspring are threatened by parasitic wasps that try to invade the nest and lay their eggs inside the cavities. This kills the baby potter wasp in the process.

Ensliniella parasitica, is a parasitic mite known to feed on the potter wasp’s haemolymph, a vital circulatory fluid that is rich in nutrients. Inside a nest, some mites move to the cavities, feeding on the food stores and the baby wasp without damaging the developing offspring. But the mite was thought to offer nothing to the potter wasps in return.

It was a surprising discovery since the mites normally show no aggressive behaviour. “None of astigmatid mites, which include this species, were previously known to attack other species, particularly ones larger than themselves,” Okabe says.

Pocket protectors

By studying the behaviour of host and mite under lab conditions, the researchers discovered that the mites will surround and kill a parasitic wasp when it enters a potter wasp nest.

The mites are not adapted to killing the parasitic wasps. Instead, Okabe suspects that they haphazardly injure the parasitic wasp by clinging onto it, in the same way that they cling to their host to feed.

The mites do not always repel an intruder successfully. If fewer than six mites attacked an intruder they were themselves killed off. Six or more mites killed the intruder 70% of the time and ten always killed it.

The Japanese study is the first of to show a mutual partnership that involves adult costs directly benefiting one partner’s offspring.

Potter wasps even have little pockets on their body called acarinaria that offer a comfy home for parasitic mites. Each acarinaria usually contains more than six mites and Okabe is now interested in working out how this magic number is maintained.